The "bigish" plug should contain all the wires for the main guages. Purple is ignition, Brown/white is trim and from memory I think the grey is Tacho, black is ground. If you link the backlights in to the ignition use blue wire (I think you get a length with the guage?). You could wire the light to your nav. light switch but I find it easier (and it looks neater) if you bridge off the ignition pole on the tacho, and daisy chain to any other guages.
I would take a pick of my console but its not in my shed anymore, ready to go backin boat